Siberia is very sparsely populated, but rich in resources. That alone makes for an interesting Age of Steam variant. On top of that, however, the permafrost offers difficulties of its own when it comes to building. This variant is an attempt to capture some aspects of Siberia in Age of Steam format. It is - quite appropriately - a very difficult map.
The most obvious rule change is that there is no urbanization. There are plenty of towns on the map, but none of them can be urbanized. At this scale none of them can be considered 'big' cities. There are three off-board cities, however: Moscow, Beijing and Vladivostok. Goods have to be delivered to these cities. Goods are produced in mines and the 'Build Mine' action replaces the 'Urbanization' action. Resource locations (where mines can be built) are shown on the map and reflect actual locations of those resources (although not necessarily the most important ones).